The "hero" who determines the black and white skin is the melanocyte located in the basal layer of epidermis and its ability to secrete melanin. However, studies show that there is no significant difference in the number of human melanocytes between different races. Normal and healthy skin color is the result of melanin synthesis and metabolic balance. Therefore, the ability to secrete melanin is strong, the amount of melanin is large, the amount of melanin deposition is large, and the skin is easy to turn black and white.
It is easy for Tan Can's skin to produce melanin in large quantities after being stimulated by ultraviolet rays. That is, when the skin is irradiated by sunlight and ultraviolet rays, the tyrosinase activity that produces black particles is enhanced, and melanocytes secrete more melanin. Because of the limited metabolic ability, the melanin deposited in the skin is increased, so it is easy to turn black. With the development of society, people's pursuit of beauty is constantly improving. At the same time, on the way to beauty, they not only shed countless sweat, but also shed many sad tears. Especially the use of heavy metal whitening products, hormone products, scrub products, skin replacement products and so on.
Laser, photon rejuvenation and other damage to the skin will lead to a decline in the ability to resist ultraviolet rays, and it is easier to stimulate the production of melanin in the skin, leading to tanning and pigmentation. Therefore, sunburn is one of the congenital genetic factors, and another reason is that human injury leads to the decline of skin ultraviolet protection ability. People who have never been tanned are characterized by the weak ability of hereditary melanocytes to secrete melanin. So even if you have been tanning, it is not easy to get tanned.